Louis de Broglie

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FRENCH PHYSICIST
1892–1987

Louis-Victor-Pierre-Raymond de Broglie was born into a noble French family. He initially studied history at the Sorbonne in Paris, intending to enter the diplomatic service. His elder brother Maurice had chosen to forgo a diplomatic career for one in physics, despite opposition from his family. Louis also became interested in science and decided to pursue a degree in theoretical physics . His plans, however, were interrupted by World War I, during which time he served in a wireless telegraphy unit stationed at the Eiffel Tower.

In 1920 de Broglie returned to his studies; later he stated that his attraction "to theoretical physics was…the mystery in which the structure of matter and of radiation was becoming more and more enveloped as the strange concept of the quantum, introduced by Max Planck in 1900 in his researches into black-body radiation, daily penetrated further into the whole of physics" (quoted by Heathcote, pp. 289–290).

During this same period de Broglie's brother Maurice was studying experimental physics, and he was particularly interested in x rays. The brothers frequently discussed x rays, and their dual nature (both wavelike and particle-like behavior) suggested to Louis that this same particle-wave duality might also apply to particles such as electrons.

In his doctoral dissertation in 1924, Louis de Broglie developed the equation λ = h/mυ , which predicts that the wavelength λ of a particle is inversely proportional to its mass m and velocity υ where h is Planck's constant.✷ The wavelength associated with a submicroscopic object—an electron, for example—is large relative to the size of the object and is therefore significant in describing its behavior, whereas the wavelength associated with a macroscopic object—a basketball, for example—is negligibly small relative to its size, and therefore the wavelike behavior of such an object is unnoticeable.

✷ See Max Planck article for more about Planck's constant.

The dual nature of electrons proposed by de Broglie, together with the dual nature of electromagnetic radiation proposed by Max Planck, led to the development of quantum mechanics by the Austrian physicist Erwin Schrödinger in 1926. The following year American physicists Charles J. Davisson and Lester H. Germer and others demonstrated experimentally that electrons can be diffracted just like light. That is, as electrons pass through a narrow slit, they spread out in a wavelike pattern similar to that of diffracted light.

De Broglie accomplished his most important work in physics while still a young man, receiving the Nobel Prize in physics in 1929. After obtaining his doctorate in 1924, he taught at the Sorbonne, and in 1928 he was named professor of theoretical physics at the Henri Poincaré Institute in Paris. In 1932 he also became professor of theoretical physics at the Sorbonne, retiring from that post in 1962.

Throughout his long life, de Broglie remained active in the development and interpretation of quantum mechanics and wrote more than twenty-five books on various topics related to this field of study. As a member of the French Commission on Atomic Energy, he was a long-time advocate for the peaceful use of atomic power. De Broglie also wrote a number of popular books to help promote public understanding of modern physics, and in recognition of these efforts, the United Nations Educational, Scientific, and Cultural Organization (UNESCO) awarded him the Kalinga Prize in 1952. He was the recipient of many awards and honors for his work in quantum mechanics.

As a young scientist de Broglie had believed that the statistical nature of modern physics masks our ignorance of the underlying reality of the physical world, but for much of his life he also believed that this statistical nature is all that we can know. Toward the end of his life, however, de Broglie turned back toward the views of his youth, favoring causal relationships in place of the accepted probabilistic picture associated with quantum mechanics.

SEE ALSO Planck, Max ; SchrÖdinger, Erwin

Richard E. Rice

Bibliography

Heathcote, Niels H. de V. (1971). Nobel Prize Winners in Physics, 1901–1950. Freeport, NY: Books for Libraries Press.

Weber, Robert L. (1988). Pioneers of Science: Nobel Prize Winners in Physics, 2nd edition. Bristol, U.K.: Adam Hilger.

Internet Resources

O'Connor, J. J., and Robertson, E. F. "Louis Victor Pierre Raymond duc de Broglie." Available from http://www.history.mcs.st-andrews.ac.uk/history/Mathematicians/Broglie.html .